1. Field of the Invention
The present invention generally relates to a differential gloss covering and method for making the same. More specifically, the present invention relates to a radiation curable floor or surface covering with a top layer exhibiting differential gloss.
2. Description of Related Art
A distinct difference between glossy and matted areas on the top surface of a covering is desirable to provide distinctive appearances. Therefore, an important feature for many coverings is the presence of selected areas or zones on the top layer of the covering that have a distinctive visual appearance compared to the remaining areas or zones. That is, a covering having differential gloss can be provided by a covering having certain areas with high gloss and other areas of low gloss or a dull, matte finish. For example, it is desirable to effect a low gloss finish on the surface overlying a particular portion of a decorative pattern, such as an imitation of a joint or grout and a high gloss finish on the remaining surface overlying the decorative pattern imitating a tile. Several methods have been developed to provide a covering having differential gloss on its surface.
U.S. Pat. No. 4,029,831 describes a method whereby an ink composition containing a curing inhibitor and solvents is applied to a base coat. The solvents are then flashed off, and a top coat is applied. In those areas of the top coat overlying the ink curing is inhibited, which produces a diffusely reflecting surface contrasted to the areas not affected by the inhibitor, which are smooth reflecting surfaces. However, the top coat is limited to an alkyd resin coating containing a polyester product with polyhydric alcohols, polybasic acids, monobasic fatty acids, and hydrocarbon solvents, the polymerization of which is an acid catalyzed or condensation polymerization reaction. As such, the inhibitors disclosed are designed to reduce the polymerization rate for this acid catalyzed system and are explicitly limited to amino methyl-propanol (AMP), hydroxyethyl-trimethyl ammonium bicarbonate, and choline.
U.S. Pat. No. 4,169,167 describes a gradient cure scheme for a radiation curable covering to produce a low-gloss finish. The gradient cure scheme includes a ultraviolet (UV) curing step in an oxygen-containing atmosphere, which actually inhibits the free radical polymerization process, to cure only the covering except for the top layer. A second UV curing step is then performed in an inert atmosphere to completely cure the top layer. Such a gradient cure scheme is thought to cause a required flatting agent to migrate to the surface of the top layer and effect a matte finish thereon upon finally curing the top layer. However, this process does not provide for differential gloss levels across the surface of the same covering.
U.S. Pat. Nos. 4,187,131; 4,214,028; 4,217,385; 4,248,922; and 4,273,819 each describe a method for effecting different surface effects in different areas of a covering. However, each of these methods utilizes mechanical embossing to provide heat to effect polymerization in some areas of the covering to cure and, thereby, permanently set the embossed, dull matte finish in those areas.
U.S. Pat. No. 4,298,646 teaches a method for obtaining differential gloss in a thermally cured top layer by adding polymerization catalysts to an ink layer that is deposited below the top layer according to a pre-selected pattern. Areas of the top layer above the ink layer containing the polymerization catalysts are then cure to a glossy finish, while other areas not above the ink layer would remain uncured. A flatting agent containing a polymerization catalyst is then dry flocked onto the top layer where it would adhere to the uncured portions of the top layer but not to the cured areas. The top layer would then be heated to thermally cure the uncured areas now containing the flatting agent to provide a cured low gloss area, thereby providing a covering having differential gloss. However, this process requires the separate addition of a flatting agent by flocking and at least two curing steps.
Similar to U.S. Pat. Nos. 4,169,167, 4,309,452 describes a process whereby differential gloss is obtained by first curing a first layer with ionizing radiation or UV light in an oxygen containing atmosphere and then applying a second layer to selected areas of the first layer and curing the entire covering in an inert atmosphere.
U.S. Pat. No. 4,491,616 describes a method for achieving differential gloss in the wear layer of a covering by applying an ink layer containing a photoinitiator only in certain areas of a substrate. Then a radiation curable layer is applied and radiation is used to cure those areas above the photoinitiator to produce a dull, matte effect. The remaining areas are then thermally cured to provide a glossy effect, thereby providing differential gloss across the surface of the covering. In addition, the substrate may contain a foamable layer, and a blowing inhibitor may be applied in the same areas as the photo-initiator. Therefore, upon foaming and curing, the non-foamed areas will correspond to, or be in register with, the dull matte areas. However, this process requires at least two curing steps.
U.S. Pat. Nos. Re. 33,069 and Re. 33,599 describe an ink layer containing a photo-initiator deposited on top of a PVC gel layer made of a PVC plastisol containing acrylic monomers. The PVC layer is gelled in an oven and solidified at a temperature low enough to prevent polymerization of the monomers. The PVC layer is passed through an embossing roll to provide mechanical impressions and a dull finish in the soft PVC layer. The PVC layer is exposed to UV radiation that polymerizes the acrylic monomer in the areas below the ink layer having the photo-initiator that has diffused from the ink layer. This polymerization xe2x80x9clocks inxe2x80x9d the dull finish on the surface in the areas below the ink layer, because the PVC layer in these areas has polyermized and is set. The PVC layer is then heated again, which causes the area not below the ink to flow such that the mechanically impressed dull finish in these areas is replaced by a smooth shiny surface. However, this process also requires two curing steps and the step of mechanical embossing.
Other methods for effecting differential gloss include U.S. Pat. Nos. 4,450,194; 4,456,643; and 5,080,954 describe methods for achieving differential gloss through the use of particles in a particular layer of the covering. U.S. Pat. No. 5,165,967 describes the use of two different coatings on the top surface to effect differential gloss.
As noted, the foregoing processes have certain disadvantages. For example, some of the foregoing processes require a mechanical embossing step prior to a radiation or UV-curing step. In addition, many of such processes require two or more curing or heating steps. Furthermore, such additional mechanical embossing or thermal treatment complicates the fabrication processes and increases the manufacturing cost of the differential gloss coverings.
Based on the foregoing, there is a need for a differential gloss covering and method therefor that do not require additional heating and mechanical embossing steps. Furthermore, there is a need for manufacturing such a differential gloss covering by a process requiring fewer steps than its conventional counterparts.
The object of the present invention is to provide a differential gloss covering and method therefor. More particularly, the covering provided by the present invention includes a differential gloss top layer that registers with an underlying print and/or embossing of the covering.
Another object of the present invention is to provide a differential gloss covering by varying microscopic chemical and/or physical structures in different areas or regions of a top layer of the covering. More specifically, the present invention provides a means for manipulating the gloss of different regions of the top layer by controlling the rate of in-situ polymerization of monomers and/or oligomers of the top layer into polymers thereof.
Another object of the present invention is to provide a differential gloss covering by varying microscopic structures of chains of polymer molecules in the top layer of the covering. Different microscopic structures of the polymer chains provide differential gloss to different areas or regions of the top layer.
Another object of the present invention is to provide a differential gloss covering by varying distribution pattern or concentration profile of a flatting agent in the top layer of the covering. Different concentration profiles of the flatting agent exhibit differential gloss in different regions of the top layer.
Another object of the present invention is to provide the foregoing differential gloss coverings while maintaining at least substantially similar or uniform macroscopic structure in its top layer. More particularly, the top layer of the foregoing differential gloss covering may be manipulated to have at least substantially similar or uniform surface configuration and/or thickness.
Another object of the invention is to provide the foregoing differential gloss coverings through radiation-initiated in-situ polymerization of the monomers and/or oligomers. More particularly, the present invention accomplishes this goal without any additional thermal, mechanical or chemical treatment of the top layer. Accordingly, the present invention allows fabrication of the foregoing differential gloss covering through fewer process steps than its conventional counterparts.
Another object of the present invention is to provide the foregoing differential gloss coverings and to treat the covering with additional chemical and/or mechanical embossing process steps to enhance the differential gloss in its top layer.
Another object of the present invention is to provide an ink composition for the foregoing coverings that manipulate the gloss in different regions of the top layer disposed thereover. More specifically, the invention provides a means for controlling the gloss by incorporating various curing agents in the ink layer.
Another object of the present invention is to provide a composition for the top layer of the foregoing coverings that can generate differential gloss by the foregoing ink compositions.
The foregoing differential gloss covering comprises a backing substrate, an ink layer, and a cured top layer having a first surface portion with a first gloss and a second surface portion, made by the process comprising providing the backing substrate; depositing an ink formulation comprising a curing agent over at least a first area of a top side of the backing substrate to form said ink layer; coating the top side of the backing substrate with a radiation curable formulation to form a top curable layer; diffusing at least a portion of the curing agent into the top curable layer; curing the top curable layer to form the cured top layer and thereby forming a differential gloss covering having said first surface portion above the first area of said top of said backing substrate having the first gloss and the second surface portion having the second gloss that is different from said first gloss.
The foregoing differential gloss coverings and methods of the present invention offer numerous advantages over prior art differential gloss coverings. First, the methods of the present invention allow fabrication of the differential gloss top layer of the foregoing covering through a single treatment step, for example, a radiation curing step. Compared with conventional fabrication methods generally requiring additional mechanical or thermal treatment steps for differential gloss, the method of the present invention does not require such additional steps. With fewer process steps, the method of the present invention is simpler and more efficient than the conventional methods. In addition, contrary to the conventional coverings which require non-uniform surface structure for differential gloss effects, the covering made by the method of the present invention manifests such differential gloss on a top layer thereof having at least substantially similar or uniform macroscopic structure across its entire region. Therefore, the method of the present invention can provide higher quality coverings with differential gloss at a lower cost. Furthermore, because the foregoing method does not involve any process step requiring extraordinary operation conditions, such a method can be readily used in conjunction with other conventional process steps such as, e.g., mechanical embossing, chemical embossing, incorporation of flatting agent and/or dyes in the top layer, and the like. Thus, the differential gloss of such a covering may be easily enhanced or augmented. Moreover, because the foregoing method provides the differential gloss covering by controlling the rate of polymerization of the curable substances in the top layer, coverings with different patterns of differential gloss may be manufactured, for example, by simply varying operational parameters for the polymerization process, such as temperature, pressure, type and concentration of the curing agents, characteristics of the radiation energy source, and the like.
Numerous embodiments of differential gloss coverings and processes of making the same described heretofore and hereinafter are applicable to general-purpose residential sheet coverings. However, such coverings and processes may also be applied to provide tiles, in particular, high-end xe2x80x9cno waxxe2x80x9d residential tiles.
The above objects as well as other objects and features of the present invention will appear from the following description from which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.